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Biomedical subjects

K Tsui

Publications and source records attributed to K Tsui.

6 recordsLinked to original sources
PubMed2005

Liver histology of Asian patients with chronic hepatitis B on prolonged lamivudine therapy.

BACKGROUND: Long-term effect of YMDD mutations on liver histology in Chinese hepatitis B patients is unknown. AIM: To examine the effect of prolonged lamivudine treatment on liver histology in Chinese patients with and without YMDD mutations. METHODS: Liver histology was assessed in 85 patients on long-term lamivudine at baseline and year 1, and at year 3 for 25 patients. RESULTS: Comparing patients with and without YMDD mutations at year 1, the former had higher baseline median necroinflammatory (11 vs. six respectively, P = 0.014) and fibrosis scores (three vs. one respectively, P = 0.001). The proportion of patients with improvement in necroinflammation and worsening of fibrosis was comparable for patients with and without YMDD mutations at year 1 (57.1%, 14.3% vs. 55%, 15% respectively) and year 3 (57.9%, 26.3% vs. 50%, 16.7% respectively). Comparing the histology at year 1 and 3, more patients with YMDD mutations developing after year 1 had worsening of necroinflammation than patients with persistent YMDD wild type (53.8% vs. 25% respectively). CONCLUSIONS: Patients who developed YMDD mutations had higher baseline histological scores. With YMDD mutations, the liver histology became less favourable after 3 years than at the first year, although there was still improvement when compared with that at baseline.

Adolescent↗
PubMed1997

Progression into the first meiotic division is sensitive to histone H2A-H2B dimer concentration in Saccharomyces cerevisiae.

The yeast Saccharomyces cerevisiae contains two genes for histone H2A and two for histone H2B located in two divergently transcribed gene pairs: HTA1-HTB1 and HTA2-HTB2. Diploid strains lacking HTA1-HTB1 (hta1-htb1 delta/hta1-htb1 delta, HTA2-HTB2/HTA2-HTB2) grow vegetatively, but will not sporulate. This sporulation phenotype results from a partial depletion of H2A-H2B dimers. Since the expression patterns of HTA1-HTB1 and HTA2-HTB2 are similar in mitosis and meiosis, the sporulation pathway is therefore more sensitive than the mitotic cycle to depletion of H2A-H2B dimers. After completing premeiotic DNA replication, commitment to meiotic recombination, and chiasma resolution, the hta1-htb1 delta/hta1-htb1 delta, HTA2-HTB2/HTA2-HTB2 mutant arrests before the first meiotic division. The arrest is not due to any obvious disruptions in spindle pole bodies or microtubules. The meiotic block is not bypassed in backgrounds homozygous for spo13, rad50 delta, or rad9 delta mutations, but is bypassed in the presence of hydroxyurea, a drug known to inhibit DNA chain elongation. We hypothesize that the deposition of H2A-H2B dimers in the mutant is unable to keep pace with the replication fork, thereby leading to a disruption in chromosome structure that interferes with the meiotic divisions.

Histones↗
PubMed1994

Accommodation of time delay variations in automatic infusion of sodium nitroprusside.

A new self-tuning regulator for control of mean arterial blood pressure using sodium nitroprusside is presented. In addition to adapting to various patient response gains and time constants, the controller can accommodate variations in pure time delays, a problem that has not been addressed fully in previously proposed controllers. The control algorithm derivation is based on incorporating a self-tuning controller with an adaptive discrete time delay compensator. The derivation, however, is general and can potentially be applied to other pharmacological agents in addition to sodium nitroprusside. The a priori information required for implementation of the controller is the estimate of the order of the patient response transfer function and the range of the pure time delay. An attractive feature of the controller is its capability to optimize the level of the infused drug during the transient phase of the control without creating an output offset. This feature tends to reduce the overall level of the infused drug. Hence, it may be useful when the cost of a drug or its long-term administration side effects is of concern, such as in the case of sodium nitroprusside.

Algorithms↗
PubMed1990

Two- and three-dimensional image reconstructions from stained and autoradiographed histological sections.

A complete system has been developed to utilize histological serial sections for two- and three-dimensional image reconstructions. Eighty to 120 sections are digitized using a personal computing system augmented with a imaging board and CCD camera. The image files are transmitted to a VAX computer for processing and image reconstruction, and the processed images are transmitted back to the personal computer for display and recording using a film recorder or PostScript printer. The software developed for the system allows serial sections to be placed into proper registration in a 256(3) array, 256 grey levels. Autoradiographs of the sections are obtained in the presence of appropriate standards which are used to recalibrate grey levels to represent linearly the radioactivity of each pixel in the sections and scale the values to allow maximum use of the grey scale. Starting from coronally sectioned material the system has been used to analyse and reconstruct rat nasal turbinates. In two dimensions horizontal and sagittal sections have been obtained while in three dimensions back-to-front and surface-rendered images have been constructed. Useful rendering of differential metabolic activity within an organ of complex geometry has been obtained, and there appears to be no reason why the system cannot be used for any material for which serial sectioning is appropriate.

Animals↗